Secondary battery which can be charged or discharged repeatedly, is wildly applied in compact and portable electronic equipment such as cellphones, laptops, etc. and in vehicles such as hybrid electric vehicles, pure electric vehicles, etc. Excessive heat will be generated in the interior of the second battery during the fast charging or high power discharging, and the electrolyte may discompose, which increases the internal pressure of the secondary battery, resulting in burning or explosion of the secondary battery, and therefore reduces the safety of the secondary battery.
In the relevant art, a contacting plate is generally provided in the secondary battery, and the contacting plate is attached onto the top cover plate, when the internal pressure of the secondary battery exceeds the reference pressure, the contacting plate deforms under the air pressure and electrically contacts with the conductive plate, which therefore results in an external short circuit between the positive electrode and the negative electrode of the cell.
However, in the above technical solution, the contacting plate is directly arranged on the top cover plate, since the top cover plate is readily influenced by external environment, for example, the cell may unavoidably expand during use, moreover, the top cover plate covers on the housing by welding and the housing will generate tensile stress on the top cover plate when expanding outward, or, welding tensile stress will be generated on the top cover plate during welding the top cover plate with the housing, etc., since the contacting plate is directly arranged on the top cover plate, thus, the contacting plate will also generate tensile stress. When being in a tensile stress state for a long time, stress fatigue will occur to the contacting plate, which may reduce the service life of the contacting plate; moreover, the tensile stress will reduce the sensitivity of the contacting plate, which causes that the contacting plate cannot act under a rated pressure, thereby reducing the safety of the secondary battery.